摘要:

In recent years there has been a growing interest in ceramic materials for high-temperature gas turbine chambers. Owing to different material properties, these gas turbine chambers have thicker walls than the metallic ones and, thus, a different geometry of the film-cooling slots, which affects the flow field. In this work the mean and fluctuating velocities and fluid temperatures have been studied numerically for two different lip-to-slot ratios. When the lip is thick, the flow becomes unsteady and a vortex street appears behind the lip; hence, unsteady computations have been carried out. The calculated results are compared with single hot-wire measurements made recently by Boman [I].

ISSN:1040-7782    

DOI:10.1080/10407789408955947

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A three-dimensional model for heat and mass transport in microscale ice lattices of dry snow is formulated consistent with conservation laws and solid-vapor interface constraints. A finite element model that employs continuous mesh deformation is developed, and calculation of the effective diffusion rates in snow, metamorphosing under a temperature gradient, is performed. Results of the research provide basic insight into the movement of heat and water vapor in seasonal snowcovers. Agreement between the numerical results and measured data of effective thermal conductivity is excellent. The enhancement to the water vapor diffusion rate in snow is bracketed in the range of 1.05-2.0 times that of water vapor in dry air

ISSN:1040-7782    

DOI:10.1080/10407789408955948

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The process of freeze coating of a polymeric melt onto a two-dimensional flat plate moving continuously in the axial direction is simulated, taking into account the limited heat capacity of the plate, the spatial variation of the plate temperature, and the heat converted from the melt to the freeze coat. To identify the controlling parameters in the process, the system of equations governing the plate temperature and the shape and the temperature of the freeze coat is transformed into dimensionless coordinates. Numerical methods have been used to solve the resulting mathematical model. The history of the spatial variation of the shape of the freeze coat is presented in graphs. The parameters controlling the shape of the freeze coat are identified, and it has been found that the plate-coat diffusivity ratio, a convective heal transfer parameter, Péclet number, Stefan number, and the fusion temperature of the molten fluid are the parameters that control the growth and decay of the Freeze-coat layer. The effect of these parameters and the boundary conditions on the behavior of the freeze-coat process is discussed.

ISSN:1040-7782    

DOI:10.1080/10407789408955949

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Laminar natural convection heat transfer is studied in a tilted fluid system consisting of multiple layers of fluid separated by solid partitions with finite thickness and conductivity. A closed form solution is derived in the limit of a thin-layered system subject to a uniform heat flux from the sides and adiabatic boundary conditions at two ends. Results are obtained in terms of overall Nusselt number Nu as a function of Rayleigh number Ra, angle of inclination of the system φ solid to fluid conductivity ratioK, thickness of the fluid layersZ,-, thickness of the solid partitions t;, and number of partitionsZϑ. The critical Rayleigh number for the onset of convection in a bottom-heated horizontal system is predicted. The results are compared with limiting cases of the problem and are in agreement. A numerical study of the same phenomenon is obtained by solving the complete system of governing equations using a finite difference formulation and a volume control method. Good agreement is found between the analytical predictions and the numerical simulation.

ISSN:1040-7782    

DOI:10.1080/10407789408955950

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The problem of mixed convection along an isothermal vertical plate in porous media with uniform surface injection or suction is studied. The analysis deals with the entire regime of mixed convection by introducing a single parameter X= [1+ (Rax/ Pex)1/2]-1where X= 1 corresponds to pure forced convection and x = 0 to pure free convection. This x parameter describes both buoyancy and forced flow effects. The nonsimilar variable ξ=(ϑ0x /α) (pex1/2+ Rax1/2)-1represents the effect of injection (ϑ0> 0 or ξ> 0) or suction (ϑ< 0 or xi < 0) at the wall. The transformed nonlinear system of equations involving these parameters is solved using a finite difference method. Results are presented for temperature and velocity profiles, local wall shear stress, and local Nusselt number for the buoyancy assisting flow condition. It is found that suction increases, whereas injection decreases, the rate of heat transfer at the wall. Correlation equations are given for the local and average Nusselt numbers.

ISSN:1040-7782    

DOI:10.1080/10407789408955951

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The problem of steady natural convection from a corrugated plate embedded in an enclosed porous medium is studied numerically. The non-Darcian effects as well as the acceleration terms are taken into consideration in the momentum equation. The governing equations in terms of vorticity, stream function, and temperature are expressed in a body-fitted coordinate system and are solved numerically by the finite difference method. Results are presented in terms of streamlines and isotherms and local and average Nusselt numbers at Prandtl numbers of 0.7 and 7.0, with Darcy-Rayleigh number ranging from 0.1 to 1000 and Darcy number ranging from 10-4to 10-1, for several aspect ratios of the cavity and plate positions. The flow and heat transfer characteristics of a corrugated plate and a flat plate are also compared.

ISSN:1040-7782    

DOI:10.1080/10407789408955952

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Steady, laminar natural convection flow from a horizontal circular cylinder with a heated core region has been theoretically analyzed by taking account of the thermal conduction of the core region. The problem is conjugate, and the main focus of the study is to examine the effect of conduction in the core region on the natural convection flow from the cylinder. The governing equations were solved numerically using a finite difference technique. The effects of various parameters are presented in graphical form. Approximate solutions for the average boundary temperature at the surface of the cylinder and for the average Nusselt number are also found. In the parametric range investigated, both the theoretical and numerical results predict nearly the same values for the average boundary temperature at the surface of the cylinder and the same values for the average Nusselt number, showing the validity of the present analysis.

ISSN:1040-7782    

DOI:10.1080/10407789408955953

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The Galerkin finite element method was applied to analyze natural convection of non-Newtonian liquids in a cylinder. The non-Newtonian liquids under consideration were assumed to obey the Carreau model. The effect of four variables, the Rayleigh number (Ra), the Carreau number (Cu), the Pradtl number (Pr) and the flow index (n) on natural convection, was examined.

ISSN:1040-7782    

DOI:10.1080/10407789408955954

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor